The present invention relates to photosensitive chips for creating electrical signals from an original image, as would be found for example in a digital scanner, copier, facsimile machine, or other document generating or reproducing device. More specifically, the present invention relates to preferably providing a supplemental photosensitive chips in abutment regions to enhance image quality.
Image sensor arrays typically comprise a linear array of photosensors which raster scan an image bearing document and convert the microscopic image areas viewed by each photosensor to image signal charges. Each photosensor collects light from a corresponding photosite. Following an integration period, the image signal charges are amplified and transferred as an analog video signal to a common output line or bus through successively actuated multiplexing transistors. One example of such an array is a charged-coupled device (CCD).
For high-performance image sensor arrays, a preferred design includes an array of photosites of a width comparable to the width of a page being scanned, to permit one-to-one imaging generally without the use of reductive optics. In order to provide such a xe2x80x9cfull-widthxe2x80x9d array, however, relatively large silicon structures must be used to define the large number of photosites. A preferred technique to create such a large array is to align several butted silicon chips, each chip defining a small linear array thereon.
The silicon chips which are butted to form a single full-width array are typically created by first creating the circuitry for a plurality of individual chips on a single silicon wafer. The silicon wafer is then cut or xe2x80x9cdiced,xe2x80x9d around the circuit areas to yield discrete chips. Typically, the technique for dicing the chips includes a combination of chemical etching and mechanical sawing. On each chip, photosites are spaced from one end of a chip to the other; the length of each diced chip from one end of the array thereon to the other requires precision dicing. It would be desirable to dice each individual chip with a precise dimension along a linear array of photosites, so that, when a series of chips are butted end-to-end to form a single page-width linear array, there is a minimum disruption of spacing from an end photosite on one chip to a neighboring photosite at the end of a neighboring chip. This minimum disruption of spacing is referred to as an abutment region. Ideally, the pitch, across an entire full-width linear array should be consistent regardless of the configuration of silicon chips forming the array. Pitch is the distance between the center points of two adjacent photosites.
Preferably, the full-width array extends the entire length of a document, such as eleven inches. Usually, the full-width array is used to scan line by line across the width of a document with the document being moved or stepped lengthwise in synchronism therewith. A typical architecture for such a sensor array is given, for example, in U.S. Pat. No. 5,473,513. When the original document moves past the full-width array, each of the photosites receives reflected light and the corresponding photosensors convert reflected light from the original image into electrical signals. The motion of the original image perpendicular to the linear array causes a sequence of signals to be output from each photosensor, which can be converted into digital data.
With the gradual introduction of color-capable products into the office equipment market, it has become desirable to provide scanning systems which are capable of converting light from full-color images into separate trains of image signals, each train representing one primary color. In order to obtain the separate signals relating to color separations in a full-color image, one technique is to provide on each semiconductor chip multiple parallel linear arrays of photosites with corresponding photosensors, each of the parallel arrays being sensitive to one primary color. Typically, this arrangement can be achieved by providing multiple linear arrays of photosites which are physically identical except for a translucent primary-color overlay over photosites for that linear array. In other words, the linear array which is supposed to be sensitive to red light only will have a translucent red layer placed on the photosites thereof, and such would be the case for a blue-sensitive array and a green-sensitive array. Although it is preferable to use three linear arrays, any number of linear arrays can be used. As the chips are exposed to an original full-color image, only those portions of the image, which correspond to particular primary colors, will reach the photosensors assigned to the primary color. Thus, the photosite determines what portions of the image will reach the photosensors.
The most common substances for providing these translucent filter layers over the photosites is polyimide or acrylic. For example, polyimide is typically applied in liquid form to a batch of photosensitive chips while the chips are still in undiced, wafer form. After the polyimide liquid is applied to the wafer, the wafer is centrifuged to provide an even layer of a particular polyimide. In order to obtain the polyimide having the desired primary-color-filtering properties, it is well known to dope the polyimide with either a pigment or dye of the desired color, and these dopants are readily commercially available. When it is desired to place different kinds of color filters on a single chip, a typical technique is to first apply an even layer of polyimide over the entire main surface of the chip (while the chip is still part of the wafer) and then remove the unnecessary parts of the filter by photo-etching or another well known technique. Typically, the entire filter layer placed over the chip is removed except for those areas over the desired set of photosites. Acrylic is applied to the wafer in a similar manner.
In the prior art, there was a problem in that the edge photosites of the chips may not capture all of the reflected light in the abutment region. Therefore, the corresponding photosensors would not convert all of the reflected light from the original image into electrical signals. Although U.S. patent application Ser. Nos. 09/039,523, 09/282,317, 09/211,761 and 09/211,765, have provided alternative techniques to improve image quality, there is a continuing need to enhance image quality by capturing as much of the reflected light from the original image as possible, so that the corresponding photosensors can accurately convert the original image into electrical signals for conversion to digital data to enhance image quality.
An assembly including a substrate; a plurality of butted photosensitive chips mounted to the substrate, wherein each photosensitive chip has an edge photosite and wherein an abutment region is formed between the edge photosites of butted photosensitive chips; and at least one photosensitive chip mounted to the substrate and butted to two photosensitive chips along the abutment region. Each photosensitive chip has a plurality of edge photosites. Each of the photosensitive chips defines a plurality of photosites evenly spaced thereon, the photosites being positioned to form a linear array on the substrate. Each of the supplemental photosensitive chips defines a plurality of photosites evenly spaced thereon.
Alternatively, each of the photosensitive chips defines a plurality of photosites evenly spaced thereon, the photosites being positioned to form multiple parallel linear arrays on the substrate. Each linear array is covered by a different translucent filter. Each of the supplemental photosensitive chips defines a plurality of photosites evenly spaced thereon, the photosites being positioned and covered with translucent filter materials to correspond with multiple parallel linear arrays formed by the photosensitive chips.
A document generating device including a raster input scanner scanning documents to generate digital image signals, the raster input scanner including a photosensitive chip assembly having photosensitive chips and supplemental photosensitive chips mounted to a substrate; a photoreceptor; a controller; a raster output scanner, being directed by the controller to expose the photoreceptor to create an electrostatic latent image based on the digital image signals received from the raster input scanner; a developer developing the latent image; a transfer unit transferring the developed image to a support material; and a fuser unit permanently affixing the developed image on the support material. The photoreceptor can be a photoconductive belt. The document generating device may further include a plurality of raster output scanners directed by the controller to expose the photoreceptor to create the latent image; and a plurality of developers, each developer applying a different color to develop the latent image.